In turbine couplings, a pair of large diameter rings are coupled together by bolts that pass through apertures in the middle of the ring web. A counter sunk through hole is provided on each of the "external" faces of the respective rings, for receiving a bolt therethrough. A series of such through holes are provided spaced at regular intervals about the ring, to provide a bolt circle all the way around the coupling. Typical bolt diameters are in the range of 2 to 33/4 inches, for example. The counter bores around the holes are typically between 4 and 8 inches in diameter, and are adapted to receive a round nut to attach to the bolt. The nut is tightened to tension the bolt stud through the middle of the through hole. As the nuts are tightened around the circumference of the coupling, sometimes a chip or burr is pulled on the face of the counter bore against which the nut rests. On later dis-assembly and prior to subsequent re-assembly of the coupling, it is desired to reclaim that surface by removing the chip before re-installing the round nuts (or whatever kind of bolt/nut combinations are being used).
Accordingly, it is desirable to be able to "face" the seat portion of the counter bore, in order to provide a smooth surface for the nut to engage with on re-assembly. However, given the relatively deeply recessed location of the seat portion, heretofore it was difficult if not impossible to fit existing facing machines into the opening. Still further, the only reference surface that is available to ensure perpendicular alignment of the facing apparatus is the bore within the bolt hole. The facing machine must be properly aligned within the opening, to ensure a square facing operation. If the apparatus is mis-aligned, then the faced portion will be at an angle, which will result in an improper fit with the nut and bolt, which can cause undesired stresses on the fasteners.